Optical information recording method, optical information recording device and optical information recording medium

ABSTRACT

The present invention provides an optical information recording apparatus and method capable of effectively determining appropriate recording parameters in a short time with favorable efficiency, when recording information onto an optical disk having different information recording conditions and information recording characteristics. An information recording condition or an information recording characteristic of an optical disk  1  is identified, and a recording pulse position is corrected at a correction accuracy according to the identifies information recording condition or information recording characteristic, such that a recording mark is formed in a predetermined position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Division of application Ser. No. 10/511,931, filedOct. 18, 2004, which is a U.S. National Stage of PCT/JP03/04874, filedApr. 17, 2003, which applications are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to optical information recording media,such as optical disks, for optically recording and reproducinginformation, and information recording methods and information recordingapparatuses that use the optical information recording media.

BACKGROUND ART

In recent years, optical disks, optical cards and optical tapes and thelike have been proposed and developed as media for optically recordinginformation. Of these, optical disks have come in for particularattention as media that are capable of recording and reproducinginformation, both in large volumes and at high density. A phasechange-type optical disk is one type of rewritable optical disk. Inorder to obtain the desired thermal and optical characteristics in phasechange-type optical disks, it is common to use a multi-layered filmconfiguration in which layers such as dielectric layers and reflectinglayers are added onto the recording layer. The recording layer that isused in the phase change-type optical disk is either amorphous orcrystalline, depending on the heating and cooling conditions caused bythe laser light, and is reversible between the amorphous and crystallinestates. The optical indices (refractive index and attenuationco-efficient) of the recording layer differ between the amorphous andcrystalline states. In the phase change-type optical disk, the twostates are selectively formed on the recording film in response to aninformation signal, and the optical changes (changes in transmittance orreflectance) that occur as a result are utilized to record and reproducethe information signal.

In order to obtain the two states, the information signal is recorded bya method such as described below. A laser light (power level Pp) that isfocused by the optical head is irradiated onto the recording film of theoptical disk in pulses (known as recording pulses) to raise thetemperature of the recording film. When the temperature exceeds themelting temperature, the recording film melts, and after the passage ofthe laser light, the melted portion rapidly cools to become an amorphousrecording mark (also known as a mark). It should be noted that the powerlevel Pp is known as the peak power. Furthermore, when the light, whoseintensity is of a level that raises the temperature of the recordingfilm to more than the crystallizing temperature and less than themelting temperature, is focused and emitted by a laser light (powerlevel Pb, where Pb<Pp) the irradiated portion of the recording film iscrystallized. It should be noted that the power level Pb is known as thebias power. Furthermore, the peak power and the bias power moregenerally are referred to as recording power.

In this manner, a recording pattern of recording marks, which arecreated from amorphous regions that correspond to the recording datasignal, and non-mark portions (also known as “spaces”), which are madeof crystalline regions, is formed on a track of the optical disk. Thus,an information signal can be reproduced, utilizing the difference inoptical characteristics between the crystalline regions and theamorphous regions.

Furthermore in recent years, use of the mark edge recording method (alsoknown as PWM recording) has increased, replacing the mark positionrecording method (also known as PPM recording). As opposed to markposition recording, in which information is only held in the position ofthe recording mark itself, in mark edge recording, information is heldin both the forward and back end of the edge of the recording mark, andthus it is advantageous for increasing the recording line density.

In the case of mark edge recording, the recording pulse during recordingof a long mark is divided into a sequence of a plurality of recordingpulses (these are known as multi pulses), and a recording method is usedin which the width of the front pulse (known as the front end pulse) ismade larger than the width of the middle pulses or the width of the lastpulse (known as the back end pulse). Considering the influence of excessheat that is transmitted from the front portion of the mark, this is inorder to lessen the distortion of the recording mark shape, and torecord a more accurate mark by reducing the heat applied to therecording film when recording the rear portion of the mark to less thanthat which is applied when recording the front portion of the mark.

Coincidentally, in the case of the mark edge recording method,differences in thermal characteristics of optical disks affect the shapeof the recording mark itself, and the degree of thermal interferencebetween recording marks. That is to say, even if recorded by the samerecording pulse waveform, the shape of the recording mark that is formedwill differ between disks. As a result, the edge of the recording markmay be offset from the ideal position, depending on the disk, and thequality of the signal that is reproduced may drop. Because of this,methods have been proposed with which a recording mark can be recordedat an ideal edge position by optimally correcting the recording power,front end pulse edge position or back end pulse edge position for anydisk.

As a method for correcting the front end pulse edge position or the backend pulse edge position, a method has been proposed in whichcombinations of code lengths that correspond to recording marks (knownas recording code lengths), and code lengths that correspond to spacesbefore or after the recording marks (known respectively as pre-codelength and post-code length) are provided in a correction table, and thefront end pulse edge position and the back end pulse edge position arecorrected according to correction values for the combinations in thecorrection table (known as correction table elements).

Furthermore, as a test recording method for correcting the front endpulse edge position and the back end pulse edge position, a method thatcorrects the front end pulse edge position or the back end pulse edgeposition has been disclosed in which before recording an actualinformation signal, a test pattern that has a specific period (known asa test pattern) is recorded, after which the test signal that wasrecorded is reproduced, and the front end pulse edge position and backend pulse edge position are corrected according to the amount of offsetof the recording mark edge determined by measuring the reproducedsignal.

It should be noted that the conventional methods described above aredisclosed in, for example, Patent Document 1 given below.

Patent Document 1: WO 00/57408.

However, in the conventional methods described above, the correctiontable for optical disks that have different recording characteristicsand recording conditions is always determined via a succession ofidentical test recording steps. Thus, if, for example, the thermalinterference of an optical disk is small, and it is not necessary tocorrect the front end pulse edge position and the back end pulse edgeposition for each element of the correction table in order to obtainsufficient reproduction signal quality, then by going through what iseffectively an unnecessary test recording step, the result is that thereis a problem in that excessive time is taken for the recording andreproduction apparatus to come to a state in which it is actuallycapable of recording an information signal.

DISCLOSURE OF INVENTION

In order to solve the foregoing conventional problems, it is an objectof the present invention to provide an optical information recordingmethod and apparatus that is capable of effectively determiningappropriate recording parameters in a short time, and accuratelyrecording and reproducing information, when recording information onto arecording medium having different information recording conditions andinformation recording characteristics.

In order to achieve this object, the optical information recordingmethod of the present invention is an optical information recordingmethod that records information onto an optical information recordingmedium, the method provides an identification step of identifying aninformation recording condition or an information recordingcharacteristic of the optical information recording media, and arecording pulse correction step of correcting a recording pulseposition, in order to form a recording mark in a predetermined position,wherein in the recording pulse correction step, correction accuracy ofthe recording pulse position is changed depending on the informationrecording conditions or information recording characteristic that wereidentified in the identification step.

The recording process of the mark can be either a mark positionrecording process, or a mark edge recording process. Correction of therecording pulse position can mean either correction of the edge positionof the recording pulse, or it can mean correction of the position of therecording pulse itself. Information recording condition means, forexample, recording density or linear recording velocity, or the like,but is not limited to these. Furthermore, information recordingcharacteristic means, for example, favorability of recordingcharacteristic, and more specifically, means for example jitter or bitrate of the reproduction signal, or repetition of the recording andreproduction characteristic, however it is not limited to these.

According to the foregoing method, since the correction accuracy of therecording pulse position is changed according to the informationrecording condition or information recording characteristic of theoptical information recording medium, it is capable of effectivelydetermining recording parameters in a short time, and can accuratelyrecord and reproduce information.

It is also preferable that the optical information recording method ofthe present invention, in which an optical information recording mediumthat has two or more information layers is used as the opticalinformation recording medium, further provides, before theidentification step, an information layer specification step ofspecifying an information layer on which the information is to berecorded in the optical information recording medium, wherein in theidentification step, information recording conditions or informationrecording characteristics of the information layer that is specified bythe information layer specification step are identified, and wherein inthe recording pulse correction step, the correction accuracy of arecording pulse position in order to record the information on theinformation layer that is specified in the information layerspecification step is differentiated according to the informationrecording conditions or information recording characteristics that areidentified in the identification step.

According to this method, the correction accuracy of the recording pulseposition is changed according to differences in the recording conditionsor recording characteristics of the information layers, and thus iscapable of effectively determining appropriate recording parameters in ashort time, and accurately recording and reproducing information.

Furthermore, in the optical information recording method according tothe present invention, in which an optical information medium that has atest recording region is used as the optical information recordingmedium, it is preferable that the method further provides a testrecording step of recording a pattern for test recording in the testrecording region, using the recording pulse that was corrected in therecording pulse correction step, and a correction amount determinationstep of reproducing the pattern for test recording from the testrecording region, and of determining the correction amount of therecording pulse position depending on the reproduction result.

Accordingly, the correction accuracy of the recording pulse position forforming the pattern for test recording is changed in accordance withdifferences in the recording conditions or recording characteristics ofthe optical information recording medium or information layers, and thusis capable of efficiently test recording in a short time to determineappropriate recording parameters, and can accurately record andreproduce information.

Furthermore, in the optical information recording method of the presentinvention, in which an optical information recording medium thatcontains a control track region is used as the optical informationrecording medium, the identification step further comprises anidentifier detection step that reproduces information from the controltrack region and detects an identifier that represents the informationrecording conditions or information recording characteristics of theoptical information recording medium, from the information that isreproduced, wherein in the recording pulse correction step, thecorrection accuracy of the recording pulse position is differentiatedaccording to the information recording conditions or informationrecording characteristics that are represented by the identifierdetected in the identifier detection step.

According to this method, by differentiating the correction accuracyaccording to the identifier that is recorded on the optical informationrecording medium, the time required for determining the recordingparameter can be shortened, and it is possible to record and reproduceinformation accurately. It should be noted that the identifier is notlimited to representing the information recording condition or theinformation recording characteristic directly, but also can representthese indirectly.

Furthermore, in the optical information recording method of the presentinvention, in which an optical information recording medium thatcontains a test recording region is used as the optical informationrecording medium, it is also preferable that the identification stepfurther provides a test recording step of recording a test recordingpattern onto the test recording region, and a characteristic assessmentstep of reproducing the test recording pattern from the test recordingregion and of assessing the information recording characteristics of theoptical information recording medium by measuring the jitter or the biterror rate of the reproduction signal, wherein in the recording pulsecorrection step, the correction accuracy of the recording pulse positionis differentiated according to the information recording characteristicsthat are assessed in the characteristic assessment step.

According to this method, even when the optical information recordingmedium does not contain an identifier, by differentiating the correctionaccuracy in accordance with the results of the test recording, the timerequired for determining the recording parameter can be shortened, andit is possible to record and reproduce information accurately.Furthermore, in this case it is also possible to test record the patternfor test recording at a low correction accuracy, and increase thecorrection accuracy by, for example, increasing the number of tableelements only when the jitter or the bitter error rate of thereproduction signal is higher than a fixed value, or conversely, it ispossible to test record the pattern for test recording at a highaccuracy, and decrease the correction accuracy by, for example,decreasing the number of table elements only when the jitter or the biterror rate of the reproduction signal is lower than a fixed value.

Furthermore, in order to achieve the object of the present invention,the optical information recording apparatus of the present invention isan optical information recording apparatus that records information ontoan optical information recording medium, that provides identificationmeans for identifying information recording conditions or informationrecording characteristics of the optical information recording medium,and recording pulse correction means for correcting a recording pulseposition, in order to form a recording mark in a predetermined position,wherein the recording pulse correction means differentiates thecorrection accuracy of the recording pulse position according to theinformation recording conditions or the information recordingcharacteristics that are identified by the identification means.

According to this apparatus, the correction accuracy of the recordingpulse position is differentiated according to an information recordingcondition or information recording characteristic of the opticalinformation recording medium, and thus is capable of efficientlydeciding appropriate recording parameters in a short time and can recordand reproduce information accurately.

Furthermore, in the optical information recording apparatus of thepresent invention, in which an optical information recording medium thathas two or more information layers is used as the optical informationrecording medium, it is also possible further to provide informationlayer specification means for specifying the information layer in theoptical information recording medium on which information is to berecorded, wherein the identification means identifies informationrecording conditions or information recording characteristics of theinformation layer that is specified by the information layerspecification means, and wherein the recording pulse correction meansdifferentiates the correction accuracy of the recording pulse positionin order to record information into the information layer that isspecified by the information layer specification means, according to theinformation recording conditions or information recordingcharacteristics that are identified by the identification means.

According to this configuration, since the correction accuracy of therecording pulse position is differentiated in accordance withdifferences in the recording conditions and recording characteristics ofthe information layers, the apparatus is capable of effectivelydetermining appropriate recording parameters in a short time, andaccurately recording and reproducing information.

In the optical information recording apparatus of the present inventionin which an optical information recording medium that contains a controltrack region is used as the optical information recording medium, theidentification means further provides identifier detection means forreproducing information from the control track region, and for detectingan identifier that represents the information recording conditions orinformation recording characteristics of the optical informationrecording medium, from the information that is reproduced, wherein therecording pulse correction means differentiates the correction accuracyof the recording pulse position depending on the information recordingconditions or information recording characteristics that are representedby the identifier detected by the identifier detection means.

According to this configuration, by differentiating the correctionaccuracy according to the identifier that is recorded on the opticalinformation recording medium, the time required to determine therecording parameters can be shortened, and it is possible to record andreproduce information accurately.

In the optical information recording apparatus of the present invention,in which an optical information recording medium that contains a testrecording region is used as the optical information recording medium,the identification means further provides test recording means forrecording a pattern onto the test recording region, and characteristicassessment means for reproducing the test recording pattern from thetest recording region and assessing the information recordingcharacteristics of the optical information recording medium by measuringthe jitter or the bit error rate of the reproduction signal, wherein therecording pulse correction means differentiates the correction accuracyof the recording pulse position according to the information recordingcharacteristics that are assessed by the characteristic assessmentmeans.

According to this configuration, even when the optical informationrecording medium does not contain an identifier, by differentiating thecorrection accuracy in accordance with the results of the testrecording, the time required for determining the recording parameter canbe shortened, and it is possible to record and reproduce informationaccurately. Furthermore, in this case it is also possible to test recordthe pattern for test recording at a low correction accuracy, andincrease the correction accuracy by, for example, increasing the numberof table elements only when the jitter or the bitter error rate of thereproduction signal is higher than a fixed value, or conversely, it ispossible to test record the pattern for test recording at a highaccuracy, and decrease the correction accuracy by, for example,decreasing the number of table elements only when the jitter or the biterror rate of the reproduction signal is lower than a fixed value.

Furthermore, in order to achieve the object of the present invention,the optical information recording medium of the present invention is anoptical information recording medium that records information, whereinthe optical information recording medium contains a plurality ofcorrection tables whose correction accuracy is mutually different andthat correspond to a plurality of information recording conditions orinformation recording characteristics.

According to this medium, since test recording is performed by directlychanging the correction accuracy of the correction table according tothe result read out from the correction table on the medium, the timerequired to determine the recording parameters can be shortened further,and information can be recorded and reproduced accurately.

It is also preferable that the foregoing optical information recordingmedium contains an identifier that represents the correction accuracy ofa recording pulse position.

According to this medium, since it is possible to test record bychanging the correction accuracy of the correction table according tothe identification result of the identifier of the medium, the timerequired to determine the recording parameters can be shortened, andinformation can be recorded and reproduced accurately.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration of a recording andreproduction apparatus according to Embodiment 1 of the presentinvention.

FIG. 2 is a block diagram showing a configuration of a recording pulseedge correction portion of the recording and reproduction apparatusaccording to Embodiment 1.

FIG. 3 is a perspective view showing a configuration of an opticalinformation recording medium according to Embodiment 1.

FIG. 4 is a flowchart that describes the operation of the recording andreproduction apparatus according to Embodiment 1.

FIG. 5 is an explanatory diagram showing an example in which a recordingpulse edge position is corrected, in Embodiment 1 and Embodiment 2 ofthe present invention.

FIG. 6 is an explanatory diagram showing an example in which therecording pulse edge position is corrected in Embodiment 1 andEmbodiment 2.

FIG. 7 is an explanatory diagram showing an example in which therecording pulse edge position is corrected in Embodiment 1.

FIG. 8 is a perspective view showing a configuration of an opticalinformation recording medium according to Embodiment 2.

FIG. 9 is a block diagram showing a configuration of a recording pulseedge correction portion according to Embodiment 3 of the presentinvention.

FIG. 10 is a flowchart that describes the operation of a recording andreproduction apparatus according to Embodiment 3.

FIG. 11 is an explanatory diagram showing an example in which arecording pulse edge position is corrected according to Embodiment 3.

FIG. 12 is a block diagram showing a recording and reproductionapparatus according to Embodiment 4 of the present invention.

FIG. 13 is a flowchart describing the operation of the recording andreproduction apparatus according to Embodiment 4.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention are described below with referenceto the drawings. The essence of the present invention is to cause achange in a correction accuracy of the recording pulse position, inresponse to various conditions such as recording characteristics andrecording conditions of a disk, in order to form a recording mark in apredetermined position. As described below, the correction accuracyincludes, for example, the number of elements in the correction tableand the resolution of the correction table, however it is not limited tothis.

Embodiment 1

In the present embodiment, identifiers representing a recording densityof a disk are assessed by reproducing the disk, and disks whoserecording density is low are recorded using a correction table that hasfewer elements. Thus, there is an advantage in not going throughunnecessary test recording steps. In the present embodiment, an exampleis shown in which the number of elements of a correction table isdifferentiated for three types of recording density, namely a first, asecond and a third recording density. The relationship between therecording densities is: (first recording density)>(second recordingdensity)>(third recording density). FIG. 1 and FIG. 2 are block diagramsshowing a conceptual structure of a recording and reproduction apparatus(optical information recording device) for realizing Embodiment 1.

The present recording and reproduction apparatus is an apparatus thatrecords and reproduces information using an optical disk (opticalinformation recording medium) 1, and is provided with a spindle motor 13for rotating the optical disk 1 and an optical head 12 that contains alaser light source (not shown) that focuses laser light onto a desiredlocation of the optical disk 1. The operation of the entire recordingand reproduction apparatus is controlled by a system control circuit 2.The recording and reproduction apparatus of the present embodimentfurther includes a table registration memory 3 that registers theinformation in the correction table into each element. It should benoted that information in the correction table can be registered in thetable registration memory 3 by read-out from the optical disk 1, or itcan be recorded in the table registration memory 3 in advance, such aswhen the recording and reproduction apparatus is manufactured. It shouldbe noted that in FIG. 1, a configuration is illustrated in which thetable registration memory 3 is external to the system control circuit 2,however it is also possible to have a configuration in which the tableregistration memory 3 is provided inside the system control circuit 2.

The recording and reproduction apparatus is provided with a test patternsignal generation circuit 4 as recording data signal generating means.In order to determine the front end pulse edge position and the back endpulse edge position, the test pattern signal generation circuit 4generates a test pattern signal for determining the edge position of therecording pulse that has a specific period, or generates a randompattern signal for generating a random pattern. Furthermore, therecording and reproduction apparatus contains a modulation circuit 5 asa recording data signal generating means that generates a recording datasignal 18, which corresponds to a recorded information signal.

The recording and reproduction apparatus further is provided with arecording pulse generation circuit 6 that generates a recording pulsesignal 19 for driving the laser, and a recording pulse edge correctioncircuit 8 that adjusts the front end pulse edge position and the backend pulse edge position of the recording pulse signal 19 that is outputby the recording pulse generation circuit 6.

A laser drive circuit 11 further is provided in order to modulate anelectric current that drives the laser light source in an optical head12, in response to the recording pulse signal 22 that is output by therecording pulse edge correction circuit 8.

Furthermore, the recording and reproduction apparatus contains areproduction signal processing circuit 14 that performs wave formprocessing of the reproduction signal, such as wave form equalization orbinary conversion that is based on light reflected from the optical disk1, as reproduction means for reproducing information from the opticaldisk 1, a reproduction signal waveform measuring circuit 16 thatmeasures the reproduction signal waveform and detects the timing of theedge of the reproduction signal waveform, a demodulation circuit 15 thatobtains reproduction information, and an identifier detection circuit 17that obtains information about the optical disk 1 from the identifiercontained on the optical disk 1.

FIG. 2 is a structural diagram showing of the recording pulse edgecorrection circuit 8 of FIG. 1 in further detail. The recording pulseedge correction circuit 8 contains a front pulse detection circuit 201that detects a front pulse from the recording pulse signal, a multipulse detection circuit 202 that detects a multi pulse, and a rear endpulse detection circuit 203 that detects a back end pulse. The recordingpulse edge correction circuit 8 also is provided with selection circuits204 and 205 for switching the number of elements in the correctiontable, first delay amount setting circuits 206 and 208 that set theamount of delay of the recording pulse edge for 32 elements, seconddelay amount setting circuits 207 and 209 that set the amount of delayof the recording pulse edge for eight elements, delay circuits 210 and211 that finally adjust the recording pulse edge and an addition circuit212 that adds the signal waveforms of the front pulse, the multi pulseand the back end pulse.

FIG. 3 shows a perspective of the optical disk 1 (optical informationrecording medium) used in the present embodiment. The optical disk 1 hasa substrate in which grooves or phase pits are formed in advance, and isfabricated by film forming such films as a dielectric film, a recordingfilm and a reflecting film (all of which are omitted from the diagram).Moreover, the substrate (also called a cover substrate) can be bonded tothe disk after film formation.

For the substrate, a transparent flat plate made of glass or resin orthe like may be used. A material in which a resin is dissolved and thencoated and dried also can be used.

As the dielectric film, it is possible to use an oxide such as SiO₂,SiO, TiO₂, MgO and GeO₂, a nitride such as Si₃N₄, BN, and AlN, a sulfidesuch as ZnS and PbS, or a mixture of these.

Material whose phase changes between amorphous and crystalline can beused as the material for the recording film, for a example SbTe-based,InTe-based, GeTeSn-based, SbSe-based, TeSeSb-based, SnTeSe-based,InSe-based, TeGeSnO-based, TeGeSnAu-based, TeGeSnSb-based orTeGeSb-based chalcogen compound. Materials such as a Te—TeO₂-based,Te—TeO₂—Au-based and Te—TeO₂—Pd-based oxide can also be used. In thecase of these materials, a phase change occurs between the crystalline(that is, corresponding to condition a) and amorphous (that is,corresponding to condition b) states. Furthermore, these also may beAgZn-based or InSb-based metallic compounds whose phase changes betweenthe crystalline state (condition a) and the crystalline state (conditionb).

Metallic materials such as Au, Ag, Al and Cu, or a multilayer dielectricfilm that has high reflectance at a predetermined wavelength can be usedas the reflective film.

As a method for film forming these materials, methods such as vacuumdeposition or sputtering can be used.

Furthermore, the optical disk 1 contains a center hole 301 for fixingthe optical disk 1 to a shaft of the spindle motor 13. The optical disk1 also contains a control track region 302, a test recording region 303and a data region 304 as its physical format.

The control track region 302 is a region for applying information thatrelates to the optical disk 1 to the optical information recording andreproduction apparatus, and it is principally reproduced when theoptical disk 1 is inserted into the apparatus. The recording structureof the information in the control track region 302 can be a structureformed in advance as phase pits in the substrate, or it can be astructure recorded as an optical transformation in the recording layer.

The control track region 302 is for applying information that relates tothe optical disk 1 with respect to the optical information recording andreproduction apparatus, and is principally replayed by the opticalinformation recording and reproduction apparatus when the disk isinserted. The recording structure of the information recorded onto thecontrol track region 302 can be a structure formed in advance on thesubstrate as a phase pit, and the structure can be recorded as anoptical change in the recording film. Information representing, forexample, the type of disk (such as single recordable, rewritable orrewritable only in a specific region), the size of the disk, recordingdensity, recording power, information about the disk manufacturer andthe correction table is recorded in the control track region 302.

An identifier 305 is recorded in the control track region 302. Anidentifier that corresponds to the correction accuracy is recorded asthe identifier 305. In this identifier, the disk manufacturer can, basedon a test result and prior to shipping, record information thatrepresents the number of elements in the correction table by whichsufficiently favorable recording and reproduction characteristics can beobtained in the optical disk 1. In the present embodiment, informationthat represents the recording density of the disk is used as theidentifier. In a similar manner to the information recorded in thecontrol track 302, the recording structure of the identifier 305 can bein the form of a phase pit, or it can be in the form of an opticaltransformation in the recording film. Furthermore, it is preferable thatthe identifier 305 is in the control track region 302, so that theapparatus can replay that information at the same time as other diskinformation when the disk is inserted. However it also can be in anyother region on the optical disk 1.

The test recording region 303 is a region for test writing, which allowsthe optical information recording and reproduction apparatus to recordonto the optical disk 1 at an appropriate recording power or recordingpulse edge position. The data region 304 is the region for recording theactual information signal.

Operation of Embodiment 1

The following is a description of the operation of the recording andreproduction device of the present embodiment using the flowchart inFIG. 4 and operational charts in FIG. 5 to FIG. 7.

FIG. 4 is a flowchart showing the operation of the present embodiment.FIG. 5 is a waveform showing the operation according to the presentembodiment when recording at an increased recording density. Theoperation to correct the edge positions of the front end pulse and theback end pulse in the combinations (that is, the elements of thecorrection table) of (pre-code length 7T-recording code length3T-post-code length 7T), (pre-code length 7T-recording code length5T-post-code length 7T) and (pre-code length 3T-recording code length5T-post-code length 6T) is described in FIG. 5. Here, T represents theperiod of the channel clock. In FIG. 5, (a) is a channel clock signal,(b) is a waveform of the recording data signal 18, (c) is a waveform ofthe recording pulse signal 19 and (d) shows a waveform of the recordingpulse signal 22 after pulse edge correction. (e) shows the state of themarks that are recorded according to the recording pulse signal, numeral501 represents a track, and numeral 502 represents a recording mark.

During test recording, first of all, according to a seek operation step(step 401 in FIG. 4, abbreviated below as S401), the optical head 12seeks out the control track region 302 on the optical disk 1, based on acommand from the system control circuit 2. The identifier thatrepresents the recording density of the optical disk 1 is recorded inthe control track region 302. Information that indicates the recordingpower and initial values of the correction table of the optical disk 1is also recorded in the control track region 302. In accordance with theinformation of the control track region 302, the system control circuit2 records the initial values of the front end pulse edge position andthe back end pulse edge position in the table registration memory 3.Furthermore, the system control circuit 2 sets these initial values inthe recording pulse edge correction circuit 8. The system controlcircuit 2 also sets the recording power of the laser drive circuit 11 inadvance.

Next, the disk information track is reproduced by an identifierreproduction step (S402), and the reproduction signal is transmitted tothe identifier detection circuit 17 via the reproduction signalprocessing circuit 14 and the demodulation circuit 15. Then, theinformation of the identifier is detected by the identifier detectioncircuit 17, and is transmitted to the system control circuit 2. In therecording density decision step (S403), the system control circuit 2decides the density at which the information should be recorded, andtransmits a switching control signal 20 that depends on the recordingdensity that was determined to the selection circuits 204 and 205 of therecording pulse edge correction circuit 8.

The results that were decided in the recording density decision step(S403) are described below, divided into the cases of the first to thirdrecording densities.

Operation of Embodiment 1 The Case of the First Recording Density

If the result of the recording density decision step (S403) is the firstrecording density (that is, the recording density is the highest), thenthe selecting circuits 204 and 205 are switched by a selection circuitswitching step (S404) to the first delay amount setting circuits 206 and208. Accordingly, a state is assumed in which the edge positions of therecording pulses can be set in response to a combination of the pre-codelength and the recording code length, and a combination of the recordingcode length and the post-code length.

The operation of the selection circuit switching step (S404) isdescribed in detail using FIG. 2. The selection circuit 204 is switchedso as to input the recording data signal 18, which comes from thedemodulation circuit 5, into the first delay amount setting circuits 206and 208. The delay amount setting circuits 206 and 208 compare a tablesetting signal 21 that comes from the table registration memory 3, thecombination of the pre-code length and the recording code length, andthe combination of the recording code length and the post-code length,and set the correction amount of the recording pulse edge in the delaycircuits 210 and 211. The delay circuit 210 adjusts the forward edge ofthe front pulse, and the delay circuit 211 corrects the edge position byadjustment of the rear edge of the back end pulse.

In this case, the structure of the correction table in the tableregistration memory 3 is as shown in Table 1 and Table 2.

TABLE 1 Forward edge correction amount Recording code length 6T and 3T4T 5T greater Pre-code 3T Δ (3, 3) F Δ (3, 4) F Δ (3, 5) F Δ (3, 6) Flength 4T Δ (4, 3) F Δ (4, 4) F Δ (4, 5) F Δ (4, 6) F 5T Δ (5, 3) F Δ(5, 4) F Δ (5, 5) F Δ (5, 6) F 6T and Δ (6, 3) F Δ (6, 4) F Δ (6, 5) F Δ(6, 6) F greater

TABLE 2 Forward edge correction amount Recording code length 6T and 3T4T 5T greater Post-code 3T Δ (3, 3) L Δ (4, 3) L Δ (5, 3) L Δ (6, 3) Llength 4T Δ (3, 4) L Δ (4, 4) L Δ (5, 4) L Δ (6, 4) L 5T Δ (3, 5) L Δ(4, 5) L Δ (5, 5) L Δ (6, 5) L 6T and Δ (3, 6) L Δ (4, 6) L Δ (5, 6) L Δ(6, 6) L greater

These tables represent the correction amount of the front end edgeposition and the back end edge position when the shortest code length is3T, and the longest code length is 11T.

Correction tables that use the same correction values for 6T and aboveare recorded as information in the control track region of the opticaldisk used in the present embodiment. Consequently, from the combinationof the code lengths, there are 32 elements in the correction tables.

A test recording and edge position determination subroutine (S405), is astep that determines the edge positions for the 32 table elements. Thedetails are described in the steps S412 to S416. That is to say that ina test pattern switching step (S412), a control signal is transmittedfrom the system control circuit 2 such that a test pattern fordetermining the correction amount of a predetermined table element canbe transmitted from the test pattern signal generation circuit 4.

By a test pattern recording operation step (S413), the recording pulsegeneration circuit 6 converts the recording data signal 18(corresponding to (b) in FIG. 5) transmitted from the test patternsignal generation circuit 4 into the recording pulse signal 19(corresponding to (c) in FIG. 5). This detects how many multiples of thechannel clock period T the signal inverted interval of the recordingdata signal 18 corresponds to, and generates a recording pulse sequenceof a predetermined number and a predetermined width at a predeterminedtiming, which depends on the recording code length.

And, in the recording pulse edge correction circuit 8, the front endpulse edge position and the back end pulse edge position of therecording pulse sequence are adjusted to the set values. That is to say,as shown in (d) of FIG. 5, the leading edge of the front end pulse of(pre-code length 7T-recording code length 3T) is adjusted byΔ_((6, 3)F), the trailing edge of the back end pulse of (recording codelength 3T-post-code length 7T) is adjusted by Δ_((3, 6)L), the leadingedge of the front end pulse of (pre-code length 7T-recording code length5T) is adjusted by Δ_((3, 5)F), . . . and thus, the pulse edges areadjusted in accordance with the values of the elements of the correctiontables of Table 1 and Table 2.

The laser drive circuit 11 carries out test recording on the track inthe test region 303 by modulating the driving current of the laseraccording to the recording pulse signal that passed through therecording pulse edge correction circuit 8, as shown in (d) of FIG. 5. Asshown in (e) of FIG. 5, after recording, the edges of the recording mark502 are formed on the track 501 at normalized positions that correspondto integer multiples of the channel clock.

After the test pattern signal is recorded, the track is reproduced bythe optical head 12 in a reproduction operation step (S414). Thereproduction signal circuit 14 carries out equalization of the waveform,and binary conversion of the reproduction signal. And, the reproductionsignal waveform measurement circuit 16 slices the binary signal, andmeasures the reproduction signal inverted interval by a signal timingmeasurement step (S415). An edge position determination step (S416)requests the difference between the reproduction signal invertedinterval and the signal inverted interval of the test pattern signal(that is, the offset amount of the edge mark), and fixes the amount thatcompensates that difference as the correction amount in that tableelement. It should be noted that the steps S413 to S416, which changethe correction amount, can be performed repeatedly until the differencebetween the reproduction signal inverted interval and the signalinverted interval of the test pattern signal is a minimum.

The system signal circuit 2 registers the edge position that is beingset in the table registration memory 3 in the system control circuit 2as edge position information, and concludes the test recording withrespect to this combination table element. Moreover, in a table elementdetermination step (S406), the system control circuit 2 determineswhether S405 has been repeated or not for all the elements of thecombination table, and completes the setting and registration of theedge position of all 32 table elements shown in Table 1 and Table 2,after which it completes the test recording and starts recording theactual information signal.

Operation of Embodiment 1 The Case of the Second Recording Density

On the other hand, when the determination result is the second recordingdensity (that is, lower than the first recording density), the operationis as described below. By a switching selection circuit step (S408), theselection circuit 204 switches so as to input the recording data signal18 that comes from the modulation circuit 5 into second delay amountsetting circuits 207 and 209. Thus, the selection circuit 204 is in acondition to set the edge position of the recording pulse, withconsideration only to the recording code length.

In the second delay amount setting circuits 207 and 209, the tablesetting signal 21 from the table registration memory 3 is compared tothe recording code length, and the correction amount of the recordingpulse edge is set for the delay circuits 210 and 211. Similarly as inthe case of the first recording density, the edge position is correctedin the delay circuits 211 and 212 by adjusting, respectively, theleading edge of the front pulse, and the trailing edge of the rearpulse.

In this case, the structure of the correction table in the tableregistration memory 3 is as given in Table 3 and Table 4. From thecombination of code lengths, the number of elements in the correctiontable is 8.

TABLE 3 Recording code length Forward edge correction amount 3T Δ3F 4TΔ4F 5T Δ5F 6T and greater Δ6F

TABLE 4 Recording code length Forward edge correction amount 3T Δ3F 4TΔ4F 5T Δ5F 6T and greater Δ6F

Furthermore, FIG. 6 is a waveform showing the operation of recording thedisk at the second recording density, according to the presentembodiment. FIG. 6 shows recording of the same recording data signal asin FIG. 5, however the operation to correct the edge position of therecording pulse is different. That is to say, correction of the edgeposition is performed with respect to a recording code length of 3T anda recording code length of 5T.

The test recording and edge position determination subroutine (S405) isthe step in which the edge position is determined with respect to the 8table elements, and is similar to that of the step for high densityrecording described above. It differs in that in the second recordingpulse edge correction circuit 9, the front end pulse edge position andthe back end pulse edge position of the recording pulse sequence areadjusted to set values. That is to say, as shown by (d) in FIG. 5, theleading edge of the front end pulse of the recording code length 3T isadjusted by Δ3F, the trailing edge of the back end pulse of therecording code length 3T is adjusted by Δ3L, the leading edge of thefront end pulse of the recording code length 5T is adjusted by Δ5F, . .. and thus, the pulse edge is adjusted according to the values of theelements of the correction tables of Table 3 and Table 4. Consequently,a table element determination step (S409) determines whether or notsetting and registration of the edge position of the eight tableelements shown in Table 3 and Table 4 is complete.

Operation of Embodiment 1 The Case of the Third Recording Density

Moreover, when the determination result is the third recording density(that is, lower than the second recording density), the selectioncircuits 204 and 205 transmit the signals to the direct delay circuits210 and 211 respectively, without carrying out the test recording.

FIG. 7 is a waveform showing the operation in the case of the thirdrecording density. FIG. 7 shows the recording of the same recording datasignal as in FIG. 5 and FIG. 6, however it differs in the correction ofthe edge position of the recording pulse. The waveforms of (c) and (d)in FIG. 7 are the same, and there is no adjustment step of the edgeposition of the recording pulse.

The method as described above is used for the following reasons. Theeffect of thermal interference between recording marks that are adjacentin the tracking direction when the disk is recorded at the secondrecording density is less than when recorded at the first recordingdensity, so fluctuations in the edge position of the recording markscaused by differences in the pre-code length or differences in thepost-code length are small enough to ignore. Consequently, the recordingpulse edges are corrected only with respect to the recording codelength, and sufficient reproduction signal quality can be obtained evenusing the correction table containing eight elements. Moreover, with thethird recording density, fluctuations of the edge position of therecording mark caused by differences in the recording code length aresmall enough to ignore. Consequently, sufficient reproduction signalquality can be obtained even without adjusting the edge position of therecording pulse with respect to the recording code length, the pre-codelength and the post-code length.

Accordingly, there are no unnecessary test recording steps whenrecording low density disks. Thus, it is possible to reduce the timetaken for test recording.

Comparative Experiment of Embodiment 1

The following is an explanation in order to confirm the effect ofEmbodiment 1, a comparative experiment (working example) in which therecording density is differentiated. A polycarbonate resin having adiameter of 120 mm and a thickness of 0.6 mm is used as the substrate ofthe optical disk 1. Unevenly-shaped phase pits are pre-formatted inadvance as a control track region on this substrate. Information thatrepresents the recording density of the disk is recorded as anidentifier in the control track region.

In order to handle recording and reproduction at different recordingdensities, an identifier that represents two different types ofrecording density is recorded on the optical disk 1. Here, informationshowing that the disk is capable of being recorded and reproduced at tworecording densities, namely at a first recording density with a minimummark length of 0.35 μm and a second recording density with a minimummark length of 0.55 μm, is recorded.

A guide groove is formed in a sector of the data region of the resinsubstrate. Furthermore, phase pits that represent address informationare formed between the sectors. The pitch of the guide grooves is 1.4μm. A protective film, a recording film, a protective film and areflective film are four layers that are film formed on the substrate bysputtering, and a protective substrate is bonded onto that. ZnS—SiO₂ isused as the protective film, GeSbTe is used as the recording film, andAl is used as the reflective film.

The disk 1 is rotated at a linear velocity of 8.2 m/s by the spindlemotor 13, and laser light of wavelength 650 nm is focused by anobjective lens whose numerical aperture (NA) is 0.6.

The power of the laser light for recording and reproduction is Pp=10.5mW, Pb=4 mW and Pr=1 mW. The modulation process of the recordinginformation uses (8-16) pulse width modulation. The frequency of thechannel clock was changed to handle the recording density.

For comparison, the case in which the number of elements in thecorrection table is 32 is shown in Table 1 and Table 2, and the casewhen the number of elements is eight is shown in Table 3 or Table 4. Thecorrection resolution of the elements is 0.5 ns. It should be noted thatcorrection resolution means the minimum unit of increase or decrease ofthe correction amount. Specific examples of the correction tables Table1 to Table 4 according to this condition, for the case in which theminimum mark length is 0.55 μm, are shown in Table 5 to Table 8, and forthe case in which the minimum mark length is 0.35 μm, are shown in Table9 to Table 12.

TABLE 5 Forward edge correction amount (ns) Recording code length 6T and3T 4T 5T greater Pre-code 3T −3 −1 −1 −1 length 4T −3 −1 −1 −1 5T −2 −1−1 0 6T and −2 −1 −1 0 greater

TABLE 6 Forward edge correction amount (ns) Recording code length 6T and3T 4T 5T greater Post-code 3T 0 2 2 3 length 4T 0 2 2 3 5T 1 2 2 3 6Tand 1 2 3 3 greater

TABLE 7 Recording code length Forward edge correction amount (ns) 3T −24T −1 5T −1 6T and greater 0

TABLE 8 Recording code length Forward edge correction amount (ns) 3T 14T 2 5T 3 6T and greater 3

TABLE 9 Forward edge correction amount (ns) Recording code length 6T and3T 4T 5T greater Pre-code 3T −5 −3 −2 −2 length 4T −4 −2 −2 −2 5T −3 −2−1 −1 6T and −2 −1 −1 0 greater

TABLE 10 Forward edge correction amount (ns) Recording code length 6Tand 3T 4T 5T greater Post-code 3T −1 1 1 2 length 4T 0 1 2 2 5T 0 2 2 36T and 1 2 3 3 greater

TABLE 11 Recording code length Forward edge correction amount (ns) 3T −34T −2 5T −1 6T and greater −1

TABLE 12 Recording code length Forward edge correction amount (ns) 3T 04T 2 5T 2 6T and greater 3

Test recording was performed using the conditions described above, afterwhich a random signal was recorded 10 times, and reproduction signaljitter was measured by a time interval analyzer. The results ofmeasuring the jitter for each information layer and correction tableelement number are shown in Table 13.

TABLE 13 Number of elements 8 32 Minimum mark 0.35 μm 11.0% 8.9% length0.55 μm 6.8% 6.5%

From Table 13, when the minimum mark length is 0.55 μm, either 8elements or 32 elements give a jitter in the 6% range. As opposed tothis, when the minimum mark length is 0.35 μm, 32 elements give a jitterin the 8% range, however it is found that in the case of eight elements,jitter deteriorates to 11.0%. This is because when the minimum marklength is 0.35 μm, the space between the recording marks is shorter andthe period of the channel clock also decreases. Consequently, sincechanges in thermal interference with respect to changes in the pre-codelength and the post-code length are relatively large, it appears thatthe desired jitter is unobtainable without using the correction tablearranged by combining the pre-code lengths or post-code lengths with therecording code length. Consequently, when the minimum mark length is0.55 μm, from the stand point of reducing the test recording time, it ispreferable to switch so that the number of elements in the correctiontable is 8, and from the stand point of obtaining a favorable jittervalue, it is preferable that the number of elements in the correctiontable is switched to 32 when the minimum mark length is 0.35 μm.

Thus, in the present embodiment, since the number of elements in thetable is reduced and the test recording is performed when recording at alow recording density according to the identification result of theidentifier of the disk, it is possible to achieve a special effect inthat the amount of time required for test recording is reduced.

It should be noted that in the embodiment described above, the number ofelements in the correction table also can be differentiated by thelinear velocity at which the disk is recorded. For example, whenrecording is performed using the same channel clock frequency, therecording density is lower at the higher linear velocity, and since heatis less likely to accumulate on the recording film during recording, theedge position of the recording mark is less susceptible to the influenceof thermal interference. Consequently, even without using the correctiontable that is combined from the pre-code length or the post-code lengthand the recording code length, a favorable jitter can be obtained. Thus,the number of elements in the correction table can be reduced, and it ispossible to reduce the time that is required for the test recording.

Furthermore, in the embodiment described above, the correction accuracywas switched by actually changing the number of elements in the table,according to the identification result of the identifier, however thepresent embodiment can also have the structure in which the correctionaccuracy is changed by keeping the number of elements in the table asis, and setting the values of the predetermined table elements to beequivalent. For example, in the tables of Table 1 and Table 2, bysetting the values of the table elements equivalent such that:Δ_((3,3)F)=Δ_((4,3)F)=Δ_((5,3)F)=Δ_((6,3)F)Δ_((3,4)F)=Δ_((4,4)F)=Δ_((5,4)F)=Δ_((6,4)F). . .Δ_((6,3)L)=Δ_((6,4)L)=Δ_((6,5)L)=Δ_((6,6)F)then the same effect of the correction table of Table 3 and Table 4 canbe obtained.

Furthermore, the adjustment step of the recording pulse edge positionwas not performed in the case of the third recording density in theoperation of the embodiment described above, however it is also possibleof uniformly adjust the recording pulse edge position withoutconsideration to the code length. At this time, the correction tablecontains a total of two elements, as shown in Table 14 and Table 15. Inthis case, it is possible to obtain more favorable recording andreproduction characteristics at the third recording density.

TABLE 14 Forward edge correction amount ΔF

TABLE 15 Rear edge correction amount ΔL

Embodiment 2

Even in a structure other than that described in Embodiment 1, and evenwhen the structure is such that the number of elements of the correctiontables differs when there is a difference in the recordingcharacteristics of the disk, it is possible to obtain a similar specialeffect. That is to say, even when the recording density is the same, ifthe disk itself has recording characteristics with low thermalinterference, then even if the number of elements in the correctiontable is reduced, the fluctuations in the edge position of the recordingmark are small enough to be ignored. Consequently, it is possible toreduce the time that is required for test recording.

An embodiment of an optical disk that has two recording layers isdescribed below, as the most typical example of the case in which therecording characteristics differ, regarding an embodiment in which thenumber of elements of the correction table are made to differ to handlethe information layers of multi-layer media.

Structure and Operation of Embodiment 2

FIG. 8 shows a perspective view of an optical disk 1 (opticalinformation recording medium) that is used in the present embodiment. Inorder to describe an internal portion of the optical disk, FIG. 8 showsthe optical disk 1 with one part cut out. The optical disk is viewedfrom the side on which the laser light for recording and reproducing theoptical disk is incident, and is made of a first information layer 801,which is positioned at the front, and a second information layer 802,which is positioned at the back. An identifier 305 is presentindependently on the information layers, and an identifier thatcorresponds to the correction accuracy is recorded.

Excluding the point that the identifier detection circuit detects theidentifier on each information layer, the configuration and operation ofthe recording and reproduction apparatus of the present embodiment isthe same as that of Embodiment 1.

Comparative Experiment of Embodiment 2

The comparative experiment (working example) of Embodiment 2 isdescribed below. The optical disk is fabricated as given below. As thesubstrate, polycarbonate resin having a diameter of 120 mm and athickness of 1.1 mm is used, and a spiral-shaped groove having a widthof 0.25 μm, a pitch of 0.32 μm and a depth of 20 nm is formed on itsupper surface. Furthermore, unevenly-shaped phase pits are pre-formattedin advance as a control track region on this substrate.

The second information layer 802 is formed on top of the surface of thesubstrate and is film formed in the order: reflective layer Ag alloy;dielectric layer ZnS—SiO₂; recording layer GeSbTe; dielectric layerZnS—SiO₂.

Next, a center layer, which transcribes a groove shape that is similarto that on the substrate, is formed. Moreover, an AlN dielectric layer,a ZnS—SiO₂ dielectric layer, a GeSbTe recording layer and a ZnS—SiO₂dielectric layer are film formed in this sequence as the firstinformation layer 801. No reflective layer is used with the frontinformation layer so as to increase its transmittance.

Finally, a sheet made from polycarbonate is bonded by an ultraviolethardening resin. The total thickness of the adhesive and the sheet is0.1 mm.

Furthermore, in the control track region of the information layers,information that represents the correction accuracy of the informationlayers is recorded in the form of a phase pit structure as theidentifier 305. The identifier information that is recorded differsbetween that of the front information layer and the back informationlayer.

The recording and reproduction experiment was performed using this disk.Rotating the disk at a linear velocity of 5 m/s, either of theinformation layers of the disk is irradiated by semiconductor laserlight of wavelength of 405 nm that is stopped down through an objectivelens, which has a numerical aperture (NA) of 0.85.

(8-16) modulation is used as the modulation code during recording andreproduction, and the signal after modulation is multi-pulse processedto cause the semiconductor laser to emit light. A mark length of 3T was0.20 μm.

For comparison, the case in which the number of elements in thecorrection table is 32 is shown in Table 1 and Table 2, and the casewhen the number is 8 is shown in Table 3 or Table 4. The correctionresolution of the elements was 0.5 ns.

Test recording was performed under these conditions, after which arandom signal was recorded 10 times, and the jitter of the reproductionsignal measured by a time interval analyzer. The result of the jittermeasurement with respect to the information layers and number ofelements in the correction table is shown in Table 16.

TABLE 16 Number of elements 8 32 Information layer Front 9.8% 8.7% Back8.3% 8.0%

From Table 16, in the information layer at the back, a favorable jitterin the 8% range can be obtained using either the correction table thathas 32 elements or eight elements. This is because there is no necessityfor the back information layer of the multi-layer media to have aconfiguration that has a high transmittance, unlike in the frontinformation layer in which it is necessary to ensure that the laserlight reaches the back layer. Therefore, because optical absorption ishigh, it is possible to constitute a multi-layer film using a thickreflecting film of a high thermal conductivity, and the heat developedduring recording tends to be dispersed easily from the recording film tothe reflecting film. Consequently, since the effect of thermalinterference in the tracking direction is small, and the change inthermal interference relative to the change in pre-code length orpost-code length is small, it seems that the jitter does not change verymuch even using a table that corrects the edge position of the recordingpulse only with respect to the recording code length. In this case,since the number of test recording process steps can be reduced when thenumber of elements is eight, it is favorable from the view point ofshortening the time required for test recording.

On the other hand, although the jitter of the front information layer isin the 8% range when the number of elements is 32, it has been foundthat this deteriorates to 9.8% with only eight elements. Since the frontinformation layer is not provided with a reflective layer that has highthermal conductivity, the heat developed during recording tends to bedispersed within the recording layer. Consequently, the change inthermal interference relative to the change in pre-code length andpost-code length is large, so it seems that the desired jitter cannot beobtained without using a correction table that is a combination ofpre-code length or post-code length and recording code length. In thiscase, it is preferable that the correction table has 32 elements fromthe stand point of obtaining a favorable jitter value.

In the present working example as described above, since the number ofelements in the correction table is reduced before test recordingaccording to the result of identifying the identifier that representsthe information layer, it is possible to shorten the time that isrequired for test recording. It should be noted that the number ofinformation layers is not limited to two, and the same result can beobtained with three or more layers, provided the number of elements ismatched to the recording characteristics of the layers.

Furthermore, the present working example is not limited to multi-layerdisks, and even with mono-layer disks, the number of elements can differin accordance with differences in the recording characteristics of eachdisk.

Embodiment 3

The present embodiment is an embodiment in which a disk whose recordingconditions are identified by reproducing an identifier on the disk, andwhose recording characteristics when, for example, the linear velocityof recording onto the disk is low, are such that even if the edge of therecording pulse is greatly changed then the effect on the edge positionof the recording mark is small, and there are no unnecessary testrecording steps to pass through by reducing the resolution of theelements of the correction table to record.

Configuration and Operation of the Embodiment 3

A structural overview of the recording and reproduction apparatus(optical information recording apparatus) for realizing Embodiment 3 isthe same as that in FIG. 1. FIG. 9 is a diagram showing the detailedconfiguration of the recording pulse edge correction circuit 8 inFIG. 1. FIG. 10 is a flowchart used to describe the operation of thepresent embodiment, and FIG. 11 is a waveform diagram of the recordingpulse signal that describes the present embodiment.

The configuration of FIG. 9 differs from Embodiment 1 in that thedestination of the transmission of the front pulse signal from a frontpulse detection circuit 901 is switched between either a first delaycircuit 908 or a second delay circuit 909 by a selection circuit 906.Furthermore, the destination of the transmission of the back end pulsesignal from a back end pulse detection circuit 903 is switched betweeneither a first delay circuit 910 or a second delay circuit 911 by aselection circuit 907. Accordingly, the number of elements in the tablesis the same, but the operation is realized by switching the setresolution of the elements in the correction table based on the diskrecording characteristics. The operation is described in greater detailusing FIG. 10 and FIG. 11.

The recording operation in FIG. 10 is as described below. The recordingdata signal 18 from the modulation circuit is transmitted to delayamount setting circuits 904 and 905. Pulse signals from the front pulsedetection circuit 901 and back end pulse detection circuit 903 aretransmitted to the selection circuits 906 and 907 respectively. In thedelay setting circuits 904 and 905, the table setting signal 21 thatcomes from the table registration memory 3 is compared to a combinationof the pre-code length and the post-code length, or a combination of therecording code length and the post-code length, so as to set thecorrection amount of the recording pulse edge for the first delaycircuits 908 and 910 and the second delay circuits 909 and 911. In thedelay circuits 908 to 911, the edge position is corrected by adjustingthe relevant recording pulse edges. At this time, for the structure ofthe correction table in the table registration memory 3 as shown inTable 1 and Table 2, the table has the same number of componentswhichever selection is made by the selection circuits.

The operation of the first delay circuits 908 and 910 differs from thatof the second delay circuits 909 and 911 in the set resolution of thedelay amount. FIGS. 11( a) and (b) show an example of an adjustment ofthe recording pulse edge by the first delay circuits 908 and 910, andFIGS. 11( c) and (d) show an example of an adjustment of the recordingpulse edge by the second delay circuits 909 and 911. Whereas the setresolution (minimum setting unit) of the delay circuit in the firstdelay circuit is r₁, that of the second delay circuit is r₂, and this ischaracterized by being smaller than that of the first delay circuit.

Furthermore, an identifier that corresponds to the set resolution isrecorded in the control track region of the optical disk 1. For example,based on the results of an examination by the manufacturer of the disk,information is recorded that shows a set resolution at whichsufficiently favorable recording and reproduction characteristics can beobtained when the edge of the recording pulse is changed, according tothe size of the effect on the edge position of the recording mark.

FIG. 10 shows a series of test recording operations. They differ fromEmbodiment 1 in the following points. In a decision step S1003, the setresolution at which the disk that is recorded can obtain favorablerecording and reproduction characteristics is identified according tothe reproduction result in an identifier reproduction step S1002. Thatis to say, in a disk that has recording characteristics whereby the edgeposition of the recording mark changes greatly when the edge of therecording pulse changes, there is an increase in the set resolution atwhich favorable recording and reproduction characteristics can beobtained.

In cases in which disks or recording conditions have recordingcharacteristics in which the edge position of the recording marks changegreatly, the selection circuits 906 and 907 are switched to the seconddelay circuits 909 and 911 in a selection step S1007, and the edgeposition of the recording pulse is adjusted and determined at therelatively fine setting resolution r₂ (corresponding to steps S1015 toS1019).

Conversely, in the case in which the change in the edge position of therecording mark of disks or recording conditions is small, the selectioncircuit 907 is switched to the first delay circuit 908 and 910 in theselection step S1004, and the edge position of the recording pulse isadjusted and determined at the relatively coarse setting resolution r₁(corresponding to steps S1010 to S1014).

By this operation, on the disk, or in the condition in which the changein the edge position of the recording mark is small, even if the stepsS1011 to S1014 are performed repeatedly while changing the correctionamount until the difference in the reproduction signal inverted intervaland the signal inverted interval of the test pattern signal is aminimum, since the setting resolution is coarse, the edge position ofthe recording pulse can be determined with a minimum of repetitions.Additionally, fluctuations of the edge position of the recording markcan be made small enough to ignore. Consequently, it is possible toshorten the time necessary for test recording.

Comparative Experiment of Embodiment 3

In order to confirm the effect of the present embodiment, a comparativeexperiment (working example) in which the linear velocity was changed isdescribed next as the recording condition. The optical disk 1 isfabricated by the same method as in Embodiment 1.

Information that represents the linear velocity at which the disk isrecorded is recorded as an identifier in the control track region. Inorder to handle recording and reproduction at different linearvelocities, two types of identifiers, which represent different linearvelocities, are recorded. Information that the disk is capable ofrecording and reproducing at linear velocities of 8.2 m/s and 12.3 m/sis recorded here.

The disk 1 is rotated by the spindle motor 13 at the two differentlinear velocities of 8.2 m/s and 12.3 m/s, and a laser light ofwavelength 650 nm is focused on the disk by an objective lens whosenumerical aperture is 0.6.

The power of the laser light is Pp=11 mW, Pb=4.5 mW and Pr=1 mW whenrecording and reproduction at the linear velocity of 8.2 m/s. When thelinear velocity is 12.3 m/s, Pp=13 mW, Pb=5 mW and Pr=1 mW. Themodulation process of the recording information used (8-16) pulse widthmodulation. By changing the channel clock to handle the linearvelocities, the minimum mark length is 0.4 μm at either linear velocity.

This comparative experiment uses the correction table shown in Table 1and Table 2. The same 32 element table is used with either of the twolinear velocities.

For comparison, the correction resolution of the table elements was setat the two types, namely 0.5 ns and 1.0 nm with respect to the linearvelocities. That is to say that the element values were set to only 0.5ns or only 1.0 ns in a setting step.

Test recording was performed using the above conditions, after which arandom signal was recorded 10 times, and the jitter of the reproductionsignal measured by a time interval analyzer. The result of the jittermeasurement with respect to the linear velocities and correctionresolution is shown in Table 17.

TABLE 17 Correction resolution 0.5 ns 1.0 Linear velocity  8.2 m/s 8.2%8.4% 12.3 m/s 8.6% 10.3%

From Table 17, a favorable jitter in the 8% range can be obtained ateither resolution of 0.5 ns or 1.0 ns for the linear velocity of 8.2m/s. Since the linear velocity is slow, it appears that changes in theedge position of the recording pulse have only a small effect on themark edge position, and thus there is not a lot of change in jitter ateither resolution. In this case, it is preferable from the stand pointof reducing the time that is required for the test recording, becausethe number of adjustment points of the pulse edge can be reduced whentest recording at the correction resolution of 1.0 ns.

On the other hand, at the linear velocity of 12.3 m/s, the jitter is inthe 8% range when the correction resolution is 0.5 ns, however it isfound that this deteriorates to 10.3% when at 1.0 ns. This is becausethe effect of the change of the edge position of the recording pulse islarge when the linear velocity is fast, and it is felt that the jitterworsens because the setting step is too coarse at 1.0 ns. In this case,from the stand point of obtaining a favorable jitter value, it ispreferable that the correction resolution is 0.5 ns.

Therefore, in recording conditions in which the change in the edgeposition of the recording mark is small, it is possible to say that bylowering the resolution based on the identification result of theidentifier, test recording is effective for accurately recording andreproducing information in a short test recording time.

In this manner, since the test recording in the present embodiment isperformed by lowering the resolution of the elements of the correctiontable, the time necessary for test recording can be shortened whenrecording under conditions in which changes in the edge position of therecording pulse have a small effect on the mark edge position.

That is to say, the present embodiment is one in which the correctionresolution is changed by switching the delay circuits. However it isalso possible to use the same delay circuits and change the resolutionfrom r₂ to r₁ by culling the setting steps, as shown in the waveform (e)in FIG. 11.

Furthermore, in the present embodiment, the number of elements in thetable is the same, without consideration of the identification result ofthe identification step, however it is also possible to change thenumber of elements depending on the recording density or recordingcharacteristics of the disk. That is to say, it is also possible to usethe combinations in the first or second embodiments.

Furthermore, in the case whereby recording conditions differ within thesame disk, test recording can be performed at a minimum testing timecorresponding to each recording condition, by recording a plurality ofidentifier information that represent a correction accuracycorresponding to the conditions. For example, as shown in Table 18, itis only necessary that the recording power, the number of table elementsand the resolution that corresponds to a plurality of linear velocitiesare recorded onto the control track region.

TABLE 18 Linear velocity v₁ v₂ Recording power P_(p1), P_(b1) P_(p2),P_(b2) Number of Table elements n₁ n₂ Resolution r₁ r₂

Moreover, if recording at different conditions within the same disk,instead of recording the number of table elements and the resolution asvalues, then it is possible to use a media to record a plurality ofcorrection tables themselves, which contain the number of table elementsand resolution. In this case, there is no necessity to provide specialidentifiers that represent the number of elements or the resolution, andthe information that is recorded in the control track region can besimplified. Furthermore, the test recording can be performed by changingthe correction accuracy of the correction table directly from the resultof the read out from the correction table on the medium, and thus it ispossible to further shorten the time required for test recording andinformation can be accurately recorded and reproduced, without needingto read out the special identifiers that represent the number ofelements or the resolution.

Furthermore, when recording a plurality of correction tables ofdiffering correction accuracies that correspond to a plurality ofdifferent linear velocities onto the medium, it is also possible toprovide a correction table for high recording densities, which has highaccuracy. In this case, since the correction accuracy can be reducedbefore test recording according to the correction table of lowcorrection accuracy, when at a low linear velocity at which the changein the edge position of the recording mark is small, it is effective inaccurately recording and reproducing information in a short testrecording time.

Similarly, when recording a plurality of correction tables of differingcorrection accuracies that correspond to a plurality of different linearvelocities, it is also possible to provide a correction table that hashigh accuracy for high recording densities. In this case, at lowrecording densities, since the correction accuracy can be reduced beforetest recording according to the correction table of low correctionaccuracy, it is effective in accurately recording and reproducinginformation in a short test recording time, in a similar manner to thatdescribed above.

Embodiment 4

The present embodiment is an embodiment in which BER is measured byrecording and reproducing a random pattern on the disk, whereby thenumber of elements in the correction table is increased and testrecording performed only when BER is higher than a fixed value, and inwhich there is no unnecessary test recording step for disks whoserecording density is low, or for disks whose thermal interference issmall.

Configuration and Operation of the Embodiment 4

FIG. 12 is a block diagram showing a structural overview of a recordingand reproduction apparatus (optical information recording apparatus) forrealizing Embodiment 4. The configuration of the recording pulse edgecorrection circuit 8 in the present embodiment can be the same as thatused in FIG. 2. FIG. 12 differs from the configuration of Embodiment 1(FIG. 1) in the provision of a BER measurement circuit 1201 instead ofthe identifier detection circuit 17.

FIG. 13 is a flowchart that describes the operation of test recording inthe present embodiment. The operation is described in more detail belowusing FIG. 12, FIG. 2 and FIG. 13.

After a seek operation (S1301) of the present embodiment, the selectioncircuits 204 and 205 are switched to the second delay amount settingcircuits 207 and 209 by a selection circuit switching step S1302. Thus,the procedure is in a state in which the recording pulse edge positioncan be set according to the recording code length.

In this case, the structure of the correction table in the tableregistration memory 3 is as Table 3 and Table 4. From the combination ofcode lengths, the number of elements in the correction table is eight.

In a similar manner to Embodiment 1, test recording and measurement ofthe reproduction signal wave form is performed in order to determine theelements in the correction table (S1302 to S1303). After determining thevalues of the eight elements of the correction table, a random signal istransmitted from the test pattern signal generation circuit 4 andrecording of the disk is performed (S1306). In addition to waveformequalization and binary conversion of the reproduction signal from thedisk in the reproduction signal processing circuit 14, the informationsignal is demodulated (S1307) in the demodulation circuit 15. Thedemodulated information signal and the information signal of the randompattern that was generated in the test pattern signal generation circuit4 are compared in the BER measurement circuit 1201, and the BER (biterror rate) of the reproduction signal is measured (S1308).

Then, the bit error rate and a BER prescribed value are compared in thesystem control circuit 2 by a BER assessment step, and the result of theassessment is obtained. Here, the BER prescribed value indicates a valueat which the bit error rate of the information that is reproduced iscapable of use. This value is fixed with consideration given to therecording margin of the recording and reproduction apparatus and theoptical disk.

If the measured value is less than the standard value, then the testrecording ends. Thus, with disks whose recording density is low, or withdisks whose thermal interference is small, if fluctuation of the edgeposition of the recording mark caused by differences in the pre-codelength or by differences in the post-code length is small enough toignore, then it is not necessary to pass through an unnecessary testrecording step. Therefore, it is possible to reduce the time taken fortest recording even when using disks that have no identifier.

If the bit error rate that was measured is higher than the BER standardvalue, then the procedure passes through the following steps. Theselection circuits 204 and 205 are switched to the first delay amountsetting circuits 206 and 208 by a selection circuit switching stepS1310. By this, the procedure is in a state in which it can set the edgeposition of the recording pulse depending on the combination of thepre-code length and the recording code length, and the combination ofthe recording code length and the post-code length.

In this case, the structure of the correction table in the tableregistration memory 3 is as given in Table 1 and Table 2. From thecombination of the code lengths, the number of elements in thecorrection table is 32.

Similarly to Embodiment 1, test recording and measurement of thereproduction signal waveform are performed in order to determine theelements of the correction table. The test recording ends afterdetermining the correction values of all the table elements.

In this manner, in the present embodiment, recording the random patternsignal after the test recording with fewer table elements, the testrecording is repeated with a greater number of table elements only whenthe BER of the reproduction signal is higher than the fixed value, andthus the procedure does not pass through unnecessary test recordingsteps when using disks whose BER recording density is low, or diskswhose thermal interference is small. Due to this, it is possible toshorten the time required for test recording even when the disk has noidentifier.

It should be noted that in the present embodiment, the decision to endthe procedure was based on the size of the BER value. However it is alsopossible to use the jitter value instead.

Furthermore, in the present embodiment, the number of elements wereincreased to perform the test recording only when the BER was higherthan a fixed value, however a similar effect can also be obtained evenin a method in which the number of elements are decreased to perform thetest recording only when the BER is lower than a fixed value. That is,the test recording time is shortened. Furthermore, in the presentembodiment, the number of elements in the correction table were changed,however a similar effect can also be obtained using a structure in whichthe resolution of the elements is changed. Moreover, a combination ofchanges to the number of elements and changes in the resolution is alsopossible.

Furthermore, the number of elements used in the correction tables of theEmbodiment 1 to Embodiment 4 is independent of the code lengths, howeversince the effect of thermal interference decreases with longer codelengths, it is also possible to use a same number of elements for codelengths over a certain length (for example 6T or more).

Furthermore, in the foregoing embodiments, the front edge position ofthe front end pulse and the rear edge position of the back end pulsewere changed in the recording pulse edge correction circuit (in thesecases, the width of the front end pulse and the width of the back endpulse change respectively), however it is also possible that the circuitadjusts the edge position by changing the actual position of the frontend pulse and the back end pulse. Furthermore, it is also possible tohave a circuit that switches between the method for changing the actualposition of the front end pulse and the back end pulse, and the methodfor changing the edge position, depending on the disk recordingcharacteristics and recording density.

Furthermore, in the foregoing embodiments, the correction accuracy waschanged according to the number of elements in the correction table, orthe value of the resolution of the correction table, however it ispossible to use any other variable as long as it is a variable thataffects the accuracy of the edge position of the recording pulse, suchas a delay amount error of the delay circuit.

Furthermore, in the foregoing embodiments, the information thatrepresents the correction accuracy was recorded on the medium as anidentifier, however it is also possible to record onto that medium theactual correction table itself that contains the correction accuracynecessary for that medium. In this case, since the test recording isperformed by changing the correction accuracy of the correction tabledirectly from the result of the read-out of the correction table on themedium, the time required for test recording can be shortened further,and information can be recorded and reproduced accurately.

Moreover, provided the optical disk is a medium in which the opticalcharacteristics of the recording mark and non-mark portion aredifferent, such as a phase change material, photomagnetic material orpigment material, then any of the methods described above can beapplied.

Furthermore, in the foregoing embodiments, recording has beenillustrated using the mark edge recording method, however the presentinvention also can be applied to the recording by the mark positionrecording method.

Furthermore, such items as the modulation method, pulse lengths andperiod of the test pattern signal are not limited to those shown in theforegoing embodiments, and it goes without saying that it is possible toset appropriate values depending on the recording conditions and medium.

INDUSTRIAL APPLICABILITY

As described above, according to the present invention, since thecorrection accuracy of the recording pulse position is changed dependingon an information recording condition or an information recordingcharacteristic of an optical information recording medium, whenrecording information on recording media whose information recordingconditions or information recording characteristics differs, it ispossible to provide an optical information recording method andapparatus that can effectively determine appropriate recordingparameters in a short time and which are capable of accurately recordingand reproducing information.

1. An optical information recording method for recording informationonto an optical information recording medium, the method comprising: arecording pulse correction step of correcting at least one element to becorrected by each resolution, which is a minimum unit of increase ordecrease of a correction amount, in order to form a recording mark in apredetermined position; wherein in the recording pulse correction step,the resolution is differentiated according to a recording linearvelocity, and the correction is performed with the correction amount,which is a total amount of at least one minimum unit corresponding tothe differentiated resolution.
 2. An information recording medium ontowhich data are recorded by recording a mark by the optical informationrecording method according to claim
 1. 3. A reproduction methodcomprising: reproducing data by reading a mark recorded on the recordingmedium by the optical information recording method according to claim 1.4. An optical information recording apparatus that records informationonto an optical information recording medium, the apparatus comprising:a recording pulse correction means for correcting at least one elementto be corrected by each resolution, which is a minimum unit of increaseor decrease of a correction amount, in order to form a recording mark ina predetermined position; wherein the recording pulse correction meansdifferentiates the resolution according to a recording linear velocity,and the correction is performed with a correction amount, which is atotal amount of at least one minimum unit corresponding to thedifferentiated resolution.